Field of the Invention
The invention pertains to the field of inner tubes for vehicle tires. More particularly, the invention pertains to a foam insert for use in tire and tube systems in bicycles, motorcycles, automobiles, trucks and other vehicles.
Description of Related Art
The susceptibility of the pneumatic tire to puncture is inherent in the nature of the elastomeric material that comprises the tire or the tire and the inner tube in the case of a bicycle or tube-type motor vehicle tire. When inflated, such elastomeric materials have the characteristics of providing both a cushioned ride and also giving greater traction than other materials, however this also has the unfortunate characteristic of having a decreased resistance to sharp objects.
Bicycle tires usually have a narrow outer rubber casing having a thin cross-section and an inner, air filled, butyl material inner tube, and they tend to be inflated to a much higher pressure than is common in motor vehicle tires. Unfortunately sharp objects can easily penetrate the outer rubber casing and puncture the inner tube. Flat tires are a common occurrence for all types of bicycles. Flat tires can be very frustrating for all classes of riders. Children's bikes with pneumatic tires can be especially bothersome. However for the adult performance rider having a flat tire especially in a remote location can be a dangerous experience leaving the rider stranded without any means of transportation. While many bike riders carry tire repair kits, tools and other devices such as air pumps and sealing materials for repairing flat tires, people often have difficulty in making such repairs especially when the need arises. In any event, penetration of the outer tire by thorns or other sharp objects resulting in the puncture of the inner tube and a flat is often a very unpleasant and frustrating experience especially if you are in a relatively remote area.
Various proposals have been made as to how this susceptibility to puncture may be avoided, with varying degrees of success. Methods which attempt to prevent puncture altogether include so-called tire liners which are attached to the inside of the tire casing or sandwiched by air pressure between the casing and an inner tube. In the past such liners have often been expensive and added significantly to the weight of the tire resulting in increased difficulty in propulsion for a cyclist.
Other solutions have sought to use solid rubber tubes in place of the air filled tube. While these do solve the problem of air loss, the high weight and lack of cushioning render the bicycle almost unrideable due to the sluggish nature and hard jarring ride that the bicycle with solid tubes imparts to the rider. Solid tubes are not accepted by any performance cyclist.
It is common to fill tires for off-road vehicles such as farm tractors or road-construction equipment with liquid, most often either water or, in colder climates, a solution of calcium chloride or ethylene glycol or propylene glycol and water. Such liquid acts as ballast for increasing traction and reducing tire wear. Finally, injected liquid solutions with small fibers in suspension have also been employed, however these are short term, heavy and quite messy to install.
Examples of prior art tires and/or tubes are as follows.
U.S. Pat. No. 4,471,827, which issued in 1984 for a “Non-pneumatic insert tube for tires” shows a non-pneumatic insert tube for a tire adapted to be mounted upon a circular rim. The insert tube is an elongated resilient plastic cylinder having a thin wall defining a continuous bore which extends throughout the entire tube length.
U.S. Pat. No. 5,795,414, which issued in 1998 for a “Puncture resistant tire assembly” shows a tire assembly for a pneumatic tire that gives a puncture resistant capability. The tire assembly includes an inner tube with an outer periphery having a plurality of protruding deflectable structures which are circumferentially continuous about the inner tube body.
U.S. Pat. No. 6,418,991, which issued in 2002 for a “Puncture proof inner tube”, provides an improved pneumatic tube formed from a semi-rigid, air-tight rubber core encased by a plurality of thin, armoring Kevlar layers bonded to the exterior wall of the core.
US Published Application No. 2010/0084064, entitled “Puncture free tire tube, puncture free tire, and method for fitting tire tube to tire” shows a puncture free tire tube to be fitted under compressive deformation into a tube housing space of an annular tire outer wall, which is detachably fitted to an annular rim, the puncture free tire tube contains a long member extrusion-molded with an elastomer as a raw material, and has a cross sectional area of from 1 to 1.3 times a cross sectional area of the tube housing space of the tire outer wall and a length corresponding to a circumferential length at a center of the cross section of the tire outer wall.
Polymer foams, as a general class, are made up of a solid and a gas phase mixed together to form a foam. This generally happens by combining the two phases too fast for the systems to respond in a smooth fashion. The resulting foam has a polymer matrix with either air bubbles or air tunnels incorporated in it, which is known as either closed cell or open cell structure. Closed cell foams are generally more rigid while open cell foams are more flexible. The gas that is used in the foams is termed a blowing agent.